Grayfox , the gun is a new Springfield . I have customized several Government models over the past few years and this is just this winters project . I usually have the guns hardchromed and so I replace all the parts except the frame , slide and mainspring housing with Brown or Wilson Bullet Proof , install Heinie or Novak sights and then bevel all sharp edges and take out tool marks before plating . I have never used an aftermarket barrel before and since I blend the slide to match the frame in back if I am going to try a different barrel now is the time so I do not have to strip hardchrome/recontour/rechrome the slide and frame later . I have a Trophy Match that came from the factory with a Stainless "Match Barrel" and it seems to have a slightly tighter fit in the frame of the new gun . I placed this barrel in the new gun and the slide overhang in the rear would have to be shortened about .030 to give a smooth transition . I tried some barrels from my other guns and all seemed to give different amounts of under/overhang so I figured the chances of finding a barrel down the road that lined the slide/frame up perfectly would be nill .I do not want to get into a timing/lockup issue by changing barrel links to try to make it line up . I installed a Wilson Match bushing on the stock barrel with a snug bushing to frame tightness and .002 barrel to bushing tightness and it shoots well but if I thought a new drop in "Match Barrel" would give a considerable advantage in accuracy/service life I would try one . I have never fit an oversize barrel that is why I am looking at the "Drop In" . Thanks , Mike...